Quality Improvement In SMT Lead Free Process With 6sigma Methodology

The electronic and electrical products play an important role in our colorful life, but we must consider the environmental protection for the continual development of our world. Lead, the most important element in the tin-lead soldering alloy, is becoming disappeared because of the harm and poison to the human beings and the environment after the used products discarded. The production quality decreased when the lead free was implemented, and the reliability of the product with lead free soldering is under study. For the EMS company, the currently most important things are how to transfer to lead free soldering completely as soon as possible and improve the high product defective rate caused by the lead-free progress, that's the focus of this paper to study.At first, this paper introduces the background of lead-free, and the status of the lead-free researching and using in the world, then compares the different of the process of the lead and lead-free according to the electronic manufacturing process, find out all potential factors leads to the decreasing of the soldering quality that cause by the higher soldering temperature of the lead-free process. Lastly using the 6sigma methodology to analyze the current lead-free products quality issues, work out the main quality issues-high reflow soldering issues, and use the proper quality improvement tools to dig out the root causes resulting in the quality problems and the key controllable factors-printing speed and pressure, and reflow soldering ramp, preheat time, soldering time, peak temperature, and find out the optimal setting for the key parameters through DOE, validating the setting through the real production, and to solve the high soldering issue in lead-free process, and achieve the target of improving the lead-free products quality, decreasing the costs and increasing the efficiency of the company and increasing profits finally.Hope this thesis will be helpful and reference for the EMS companies in the transition from lead process to lead-free process, in the field of quality improvement methodology and in the future research directions.